1. Field of the Invention
The present invention relates to an apparatus and method of measuring bone mineral density and bone strength and, more particularly, to the use of pleochromatic X-rays for such measurements.
2. Description of Related Art
A method of diagnosing osteoporosis and renal osteodystrophy of dialysis patients, by, for example, measuring the bone mineral density, is known in the prior art. As shown in FIG. 5, an X-ray tube 31 receives power from a stabilized power source for applying an appointed voltage to the X-ray tube 31. The resulting X-rays are filtered by an X-ray filter 33, and collimated by a primary collimator 34. A support 35 for supporting an object 36 to be measured locates the object 36 adjacent an X-ray detector 38. A secondary collimator 37 finally defines the path of the transmitted X-rays 42 through the object. The resulting measurement signals can be processed by a signal-treating portion 39.
In the above-described construction white (continuous) X-rays 40, emitted from the X-ray tube 31, are turned into monochromatic secondary X-rays 41 by passing through the X-ray filter 33. They are then incident upon the object to be measured, for example, a waist portion of the human body, through the primary collimator 34. The incident secondary X-rays 41 are transmitted through the object to be measured 36 and, while being absorbed by bone material in the object result in the transmitted X-rays 42. The transmitted X-rays 42 are detected by the X-ray detector 38 through the secondary collimator 37. The detected signal is treated in the signal-treating portion 39.
A NaI (Tl) scintillator, a CdWO.sub.4 scintillator, a CdTe semiconductor detector and the like has been used as the X-ray detector 38 so that only the transmitted X-rays 42, which have passed through the object to be measured 36, can be detected. As a result, although data on the bone mineral density (quantity of bones) are obtained, data on the bone strength (condition of bones), indicating a content of crystalline ingredients in the bones, cannot be obtained. Thus, the bone strength has been estimated from the data on the bone mineral density, and the above described diagnosis has not always been accurate.
The prior art is still seeking to optimize the measurement of bone mineral density and bone strength.